HF and UV-ozone integrated wafer preclean: chemistry and effects on thermal gate oxide

Abstract

Monolayer amounts of contaminants or surface residues after silicon surface cleaning are shown to have significant impact on the electrical integrity of simple test device structures. Si surfaces are exposed to controlled amounts of various chemical species, such as hydrocarbons, oxide, hydrogen, or fluorine, using an integrated processing system with in-situ analysis capability. Thermal oxides are grown in-situ on those surfaces and poly or metal-gate capacitors are fabricated. Some surface species, such as carbon, are found to be detrimental to the oxide quality after processing, whereas others enhance it's properties, e.g., fluorine. Process integration sometimes enhances device sensitivity to molecular contaminants because these species are preserved throughout processing.